1. Field of the Invention
This invention relates to honeycomb useful in high temperature environments that has been shaped such that the face of the honeycomb has an area of curvature that has at least two points that are located in different tangential planes. In a preferred embodiment this invention relates to honeycomb having a curved shape.
2. Description of Related Art
U.S. Pat. No. 5,096,526 discloses a process for forming a shaped structure from a high melt temperature thermoplastic laminate and a honeycomb core and particularly a process for bonding a thermoplastic laminate to a honeycomb core and subsequently shaping the structure on a molding tool. The process involves heating the laminate to more than 600° F. (315° C.) to bond the thermoplastic laminate coversheets to the honeycomb core without adhesives and then shaping the coversheets with the honeycomb core.
U.S. Pat. Nos. 5,137,768; 6,544,622; and 5,789,059 disclose honeycombs made from sheets made from high modulus para-aramid materials. These honeycombs are highly prized due to their high stiffness, high strength-to-weight ratio, and temperature resistance. The high modulus of the para-aramid materials can create very stiff honeycomb, which is desirable in many instances, but can create problems when trying to mold these honeycombs into curved shapes. When the honeycomb is shaped over or in a form having an area of curvature, one face of the honeycomb is put in tension and the other in compression. The side in compression generally suffers more damage and this damage is generally a recurving of cell walls; that is, a collapsing or bending of cell walls into the cell. If a large number of the cells have recurved cell walls the honeycomb has a serious structural defect.
Therefore what is needed is a honeycomb containing high modulus materials that also is able to withstand molding without damaging an excessive number of honeycomb cells.